Observable#unbind: unbinding attribute which is not bound throws ambiguous error

[Reinmar]

Moved from https://github.com/ckeditor/ckeditor5-core/issues/153

A.bind( 'x' ).to( B, 'a' );
A.unbind( 'totallyNotBoundToAnythingOrEvenNotExistingInA' );

Actual: TypeError: Cannot read property 'to' of undefined

Expected: A meaningful error.

[jodator]

I've just stumbled upon this. Still an issue... as in my feature I'm binding/unbinding stuff and there is no way to check if a binding already exists (AFAIK).

[oleq]

IMO unbinding a non-existent attribute should not throw an error. Since o.unbind() does not throw, neither o.unbind( 'nonexistent' ) should throw.

[oleq]

Still an issue... as in my feature I'm binding/unbinding stuff and there is no way to check if a binding already exists

Just to be clear, this sounds like another problem. If you meant double bindings like

A.bind( 'x' ).to( B, 'a' );
A.bind( 'x' ).to( B, 'a' ); // -> this one throws

this should be a separate issue. Perhaps we should not throw in such situation.

[jodator]

@oleq I'm describing problem from you first comment:

const a = new ObservableClass();
a.unbind( 'foo' ); // whoopsie :(

On the second I don't have an opinion... maybe it is OK to throw as we allow only one binding per attribute.

[jodator]

OK. I've created a rather simple fix for that issue only.